anyone know about car radios? I'm stumped

[mattstead]

ok, not exactly kitcar specific, but if anyone can work this out it's you lot.

I'm trying to install a cd player and can't get the speaker wiring right. The car just has bare wires so I'm wiring in a standard iso adapter. I've got the power correct and have identified the speaker wires as I can listen to each one in turn but when I wire them all in I get sound for about 1 minute and then it goes silent...if I then cut the wires to some of the speakers I get audio again but it is very spluttery and quiet.

Anyone knows what's going on? If I have the polarities of the speakers the wrong way round is it possible that it builds up some sort of resistance or capacitance? I've tried another radio in it and thatdoes the same.

[migwell]

I have seen this before where to many speaker were wired into 1 channel, this overloaded the output chip

1 how many speakers are you running
2 are they wired individually, as they should be (ie.4x35watt means 4 speakers)
3 what is the stereo output
4 are you trying to power large speakers with low output and tiny cable

just a few questions may help

[mattstead]

migwell said:

I have seen this before where to many speaker were wired into 1 channel, this overloaded the output chip

1 how many speakers are you running
2 are they wired individually, as they should be (ie.4x35watt means 4 speakers)
3 what is the stereo output
4 are you trying to power large speakers with low output and tiny cable

just a few questions may help

thanks for the response:

1. running 4 speakers (2 front, 2 rear)
2.I believe they are individually wired with a pos and neg per speaker.
3. I need to have a look tommorow to confirm, but I think it's a 4 x 35 watt.
4. Not large speakers, just factory standard cheapy ones found in an average car.

[Mr2Mike]

Use a multimeter to check if any of the speaker cables have been grounded. This can happen through chafing, or more usually where someone has stuck a self tapping screw through one.

[migwell]

yep,as previously said, sounds like a wire is going to ground/earth, doesnt need to be touching much, also check as the speakers go into there holes nothing is touching the spade connectors and shorting there.

[Stubby Pete]

migwell said:

yep,as previously said, sounds like a wire is going to ground/earth, doesnt need to be touching much, also check as the speakers go into there holes nothing is touching the spade connectors and shorting there.

+1
Almost certainly a short on one or more of the cables, either to each other or to earth.
Try removing speakers and wiring them up on the seat, if the same problem persists, new speakers or new stereo!!

[Bi22le]

I use to do this thing all day!
Depending on the stereo it will be to many speakers (too much resistance) or a grounded wire (as said above). The radio is cutting out to prevent damage and the quite noise and distorted returned noise is probably due to hot components inside the radio. Check the speakers individually with a multimeter. You can also 'pop test' each one with any battery (12v or less, cant be watch batteries). All you do is get the two wires, one on one terminal and dab the other terminal with the wire. Don’t hold it on. An AA battery will be fine.

Also for your information on the ISO plug, The colours are:
grey: Front right
White: Front left
Purple: Rear right
Green: Rear left

Black stripe of each colour is normally negative. As long as you do them all the same though it don’t really matter.

hope that’s ok.

[mattstead]

great advice from everyone, Many thanks.

I hope to fix it later today.

[Mr2Mike]

Bi22le said:

I use to do this thing all day!
Depending on the stereo it will be to many speakers (too much resistance)

The problem comes from connecting speakers in parallel which gives too low an impedance.

[mattstead]

Thanks for everyones help, turns out a speaker wire had been chaffing and had gone to earth.

The test with the AA battery to find which speaker is which was great too.

thanks.